JPH05307636A - Method and device for scanning bar code at variable speed - Google Patents

Abstract

PURPOSE: To improve the percentage of success in reading by a scanner by increasing or decreasing the rotating speed of a motor in response to the detection of the minimum bar-space width scanned by the scanner. CONSTITUTION: An optical scanner is incorporated with a scanning module 24 and a printed circuit board 26. A microprocessor 50 generates a control signal upon detecting the distance between continuous bars/spaces and sends the signal to a motor driving speed control circuit 54 through a bus 52 and the circuit 54 generates a motor control signal to a motor 32 through a line 56 in response to the generation of each control signal. Namely, the microprocessor 50 decides whether or not the minimum bar/spacer tag piece permitted to the bar code is detected and, when it is indicated that the generating time of the continuous bars and spaces is shorter than a preset one and the printed numbers of bars and spacers on a bar code label are excessive or insufficient, and so on, the scanning speed of the scanner is decreased by reducing the speed of the motor 32 by causing the armature winding of the motor to output a signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical bar code scanning systems, and more particularly to bar codes having bar / space distances less than the required minimum and suitable for bar codes remote from the scanner. A method and apparatus for operating a bar code scanner for reading.

[0002]

2. Description of the Related Art Today, in commercial operations at the point of sale, merchandise purchase data is printed on the merchandise or is obtained by reading a data-encoding sign such as a bar code label on the merchandise. To standardize the bar codes used in various sales accounting systems, the food industry has adopted the Unified Product Code (UPC).
It is in the form of a barcode consisting of a series of bars and spaces. In multiple bar codes such as UPC, each digit is represented by two pairs of vertical bars and spaces in a 7-bit pattern. In this case, a binary 1 bit represents a black module or bar of expected width and a binary 0 bit represents a bright module or space. The scanning system works well for scanning standard size UPC labels on flat surfaces, but if there are overprinted or underprinted bars, spaces on these UPC labels, it will be If the distance to the space is changed and the label is shortened to allow it to be placed on small items such as gum, or the label is placed at a greater than normal distance from the scanning device,
The reading efficiency of the scanning system is unacceptably low.

[0003]

SUMMARY OF THE INVENTION Therefore, the present invention projects and scans a scan pattern so that over- or underprinted labels or even very small bar code labels can be efficiently scanned. It is an object of the present invention to provide an improved scanning system that can provide a deep depth of focus that allows the label to be read regardless of the label size or position with respect to the device.

Another object of the present invention is to read over or underprinted bar code labels or truncated bar code labels.
s) reading is to provide an improved scanning system which controls the scanning speed of the scanning pattern.

Yet another object of the present invention is to provide a scanning system that detects the size of a bar code label in response to reading the bar code label and automatically controls the scan speed of the scan pattern.

Yet another object of the present invention is to provide a scanning system that is inexpensive and yet has high reading efficiency.

[0007]

To achieve the above objects, a scanning device is provided which can be mounted on a handheld scanner. The scanner device includes a motor for rotating a hollow drive shaft. The drive shaft rotates about an axis of rotation that extends through the motor. Adjacent to one end of the drive shaft is a laser that projects a laser light beam along a rotational axis that extends through the drive shaft. At the other end of the drive shaft, a deflecting member arranged so as to cross the rotation axis at a certain inclination angle is mounted. The deflecting member deflects the laser light beam outward toward the ring-shaped pattern forming mirror. The patterning mirror projects a scanning pattern for scanning the barcode label. The light reflected from the barcode label is converted to an electrical signal and sent to a microprocessor which decodes the electrical signal into a binary signal representing the data stored on the barcode label. The speed of the motor is controlled by the signal applied to the motor.
When the microprocessor receives data representing the light and dark bar pattern of the bar code label, the microprocessor detects the bar-to-space distance of the bar code which indicates the position and size of the label with respect to the focal plane of the scanning system. In response to detecting the minimum bar / space width scanned by the scanner, the microprocessor controls the signal applied to the motor. The microprocessor reduces the rotational speed of the motor. This action correspondingly reduces the speed of the scanning beam across the bar code label and reduces the input frequency of the bar code signal detected by the scanning system. This action effectively normalizes the information towards the low frequencies of the minimum bar / space data by lowering the frequency of the incoming information. If after a period of time the minimum bar / space value is not detected, the speed of rotation of the motor is returned to its maximum speed.

Those skilled in the art will clearly understand the present invention and its problems, features, and advantages from the following detailed description and the accompanying drawings. Like numbers in some of the drawings indicate like or corresponding parts.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a UPC code or an encoded label (hereinafter, referred to as an encoded label) 20 is schematically shown. The UPC label 20 consists of a series of light and dark parallel bars and contains 12 characters. Two of the twelve characters are the industry code and the modulo check character, and the remaining ten are the main code representing the numeric data associated with the product. This data typically represents the item identification data used to obtain the price of the item. As shown in FIG. 1, this label contains readable numbers printed in OCR-B font. In addition to a series of light-dark parallel bars, the UPC code contains spaces that are read on both sides as left and right margins. Other properties of the UPC code include: (1) The overall shape of the symbol is a rectangle. (2) Each character of the UPC code is represented by two black dark bars and two light spaces. (3) The continuous light and dark parallel bars include a central strip-shaped pattern located at the center of the UPC code and separated from the margin by the left and right guard patterns provided on both sides.

Referring to FIG. 2, there is shown a schematic diagram showing details of an optical scanner used to practice the method of the present invention. In this figure, the optical scanner is generally designated 22
And includes a scanning module 24 and a printed circuit board 26. The scanning module 24 includes a laser 28 located adjacent one end of a drive shaft 30 driven by a motor 32. A motor 32 is provided at the opposite end of the drive shaft 30.
Optical transceiver 3 that extends diagonally
4 are provided. The transceiver directs a laser light beam 36 outwardly toward a ring-shaped mirror 38 that forms a scanning pattern for scanning a bar code label 40.
And a condensing portion 41 that condenses the reflected light beam 42 from the bar code label 40 and directs this light beam to a photodetector 44. The photodetector 44 is mounted on a video board 46 and produces an electrical signal upon receiving the reflected light beam in a manner known in the art. This electrical signal is transmitted via line 48 to a microprocessor 50 mounted on printed circuit board 26 for decoding. As will be described in more detail below, the microprocessor 50, in response to detecting the continuous bar / space distance, generates a control signal and sends this signal to the motor drive speed control circuit 54 via the bus 52. Circuit 54 generates motor control signals for motor 32 via line 56 in response to the generation of these control signals. The construction of the scanning module 24 is disclosed in U.S. Pat. No. 4,971,410 to Wyck et al., Assigned to the assignee of the present invention.

Microprocessor 50 processes this decoded signal via coiled cable 58 to a remote processing unit 60.
Send to. The laser 28, motor 32, and photodetector 44 are powered via electrical plug 62 and cable 58. The printed circuit board 26 further includes a speaker 64 and circuitry for operating the green and red indicator lights 66,68. These indicator lights indicate whether the reading is valid or invalid.

Referring to FIG. 3, a schematic diagram of circuit 54 (FIG. 2) and motor 32 is shown. Motor 32
Includes a three-phase brushless DC motor 70. The motor 70 comprises three sets of equally spaced armature coils 72, 74, 7 connected to a bus driver 84 by conductors 78, 80, 82.
Including 6. Since the bus driver 84 rotates a rotor (not shown) at a constant speed, the set of armature coils 72
Supply the required voltage to -76. As the bus driver, an integrated circuit chip of model number "74AC125" manufactured and sold by National Semiconductor or Hitachi can be used. This chip has a quiescent current (qu
iescent current) is only 2 microamps, which is 1000 times smaller than prior art triple half bridge circuits. This integrated circuit chip 74AC
The 125 is a four-gate chip designed for use as a computer system memory bus driver.

Bus driver 84 is connected to microprocessor 50 by a group of control lines 86-96 on bus 52 (FIG. 2). The microprocessor 50 is a commutation logic (commut) required for the operation of the motor 70.
ation logic). The hall sensing unit 98 is
Three Hall sensors 100, 102, 104 separated by 60 degrees and connected to lines 106, 108, 110 respectively.
including. A 5 volt power supply 112 powers the Hall sensing unit 98 via line 113 and the bus driver 84 and exclusive OR gate 118 via lines 114,116. Hall sensing unit 98 detects rotor motion and sends a signal indicative thereof to microprocessor 50 and exclusive OR gate 118 via lines 122-126.
(One of the inputs of gate 118 is connected to the output line via line 120). The exclusive OR gate 118 is connected to the line 1 when any Hall sensor detects a change in the position of the rotor.
An interrupt signal is output to the microprocessor 50 via 28. The movement of the rotor is thus monitored after every 360 degrees of rotation.

Referring to FIG. 4, details of the connection of circuit 54, bus driver 84 and motor 70 to armature windings 72-76 are shown. Armature winding 72-76
Are shown to be connected to leads 78-82, respectively. Each of the above lines is gate 1 in chip 84
It is connected to 30-134. These gates are 3-state gates, each with one output and two inputs (inputs 136 and 138 for gate 130 and input 140 for gate 132).
And 142, inputs 144 and 14 for gate 134
6). Each gate is a normal triple of the prior art
Half-bridge circuit P-channel hex FET
(Hexfet) and N-channel hex FETs. Input signals MDR1-MDR6 are provided by microprocessor 50 (FIG. 2) and control the operation of the gates for source and sink currents through the motor drive windings.

A 5 volt power supply 148 is connected to the chip 84 via line 150 and is also grounded to a 0.01 microfarad capacitor 152 and three parallel lines 15.
It is connected to 4-158. Lines 154-158 each include a pair of diodes 160-162, 164-166, and 168-170. Three lines 154-158 form lines 78-82 and node points 172-176, respectively. Line 15
4-158 is also connected to ground, and line 17
8 to the bus driver 84.

Input signals MDR1, MDR2 and MDR
3 is another gate input signal MDR4, MD when the logic value is low
It is an enable signal that causes the values of R5 and MD6 to appear at the gate output terminal. When the enable signal is logic high, the associated gate “floats” (high impedance state),
No source or sink current flows. Drive winding 72-
Reference numeral 76 appropriately receives the source current under the control of the input signals MDR1 to MDR6, flows the sink current, and drives the motor armature. For example, to pass a source current to winding 72 and a sink current from winding 74, the signal MDR
1, MDR2 and MDR5 must be low and MDR3 and MDR4 must be high and MDR6 can be high or low. As another example, signals MDR2, MDR3, MDR6 are low and MDR1, MDR6 are low in order to source current into winding 74 and sink current from winding 76.
DR5 must be high and MDR4 can be high or low. It will be appreciated from this configuration that the microprocessor 50 can control the rotational speed of the motor 70 through the input signals MDR1-MDR6.

Referring to FIG. 5, the microprocessor 5
A flow chart of 0 operations is shown. When the microprocessor 50 powers up the scanner to obtain tag information (block 180), the time-out period (tim
(e-out period) is started (block 181). The microprocessor 50 then determines the scheduled time corresponding to the smallest bar / space tag strip allowed for the bar code,
By comparing the time of occurrence of consecutive bars and spaces, it is determined whether the smallest bar / space tag piece was detected (block 182). If the occurrence time of continuous bars and spaces is shorter than the scheduled time and the bar and space on the bar code label 40 (FIG. 3) is in the excessive or insufficient printing state,
Or, if the label is shown to be shortened or located outside the focal plane of the scanner, the microprocessor will send the appropriate input signal MDR to gates 130-134.
1-MDR6 is generated causing a signal to be output to the armature winding 72-76 via line 78-82. This reduces the motor speed (block 184) and reduces the scan speed of the scan pattern, allowing the scan pattern to sense bars and spaces on the bar code label. The microprocessor then determines whether the bar code tag was successfully read (block 19).
0). If so, the microprocessor follows path 192 to activate speaker 64 (FIG. 2) and indicator light 66 (block 194) to indicate a successful read. Since no successful read of the tag has occurred at this point, the microprocessor checks to see if the time-out period has expired (block 196) and if it has not, through path 198 the smallest bar / space tag strip. Is detected (block 182). If no minimum bar / space tag strips are detected after a predetermined time, the microprocessor follows path 186 and selects the appropriate input signal MDR1-MDR6 for proper scan operation.
The motor speed is increased by generating (FIG. 4) (block 188). If the time-out period has expired, the microprocessor terminates scanner operation (block 200).

[0018]

[Effect] With this configuration, the scanning speed of the scanning pattern for scanning the barcode label is changed based on the printing condition of the bar and the space on the label, the position of the barcode label with respect to the scanner, or the shortening of the label, and the scanning by the scanner is successful. It will be understood that the rate will increase.

That is, the present invention projects a scan pattern to enable efficient scanning of over- or under-printed labels or even very small bar code labels, as well as the size of the label for the scanning device. It is possible to provide a deep depth of focus that allows the label to be read regardless of the position.

According to the present invention, when reading a bar code label printed excessively or insufficiently or reading a shortened bar code label, the scanning rate of the scanning pattern can be controlled to increase the reading rate of the scanner.

The scanner of the present invention can detect the size of the bar code label and automatically control the scanning speed of the scanning pattern.

Further, the present invention can provide the scanning system having the above high reading efficiency at a low cost.

[Brief description of drawings]

1 is a diagram representing a coded symbol or coded label, such as a UPC code symbol.

FIG. 2 is a schematic diagram showing details of an optical scanner used to carry out the method of the present invention.

FIG. 3 is a schematic diagram of a motor drive circuit.

FIG. 4 is a schematic diagram of a control circuit for a scanner motor.

FIG. 5 is a flow chart of the operation of the scanner according to the present invention.

[Explanation of symbols]

 20 Coded Label 22 Optical Scanner 24 Scanning Module 26 Printed Circuit Board 34 Optical Transceiver 36 Laser Light Beam 38 Mirror 40 Bar Code Label 54 Motor Drive Speed Control Circuit 60 Processor 64 Speaker 66, 68 Indicator Light

Claims (2)

[Claims] 1. A scanning light beam source projected along a spin axis, a deflection means for deflecting the scanning light in a scanning direction to scan a bar code label including a bar and a space, and a device mounted on the spin axis. An optical scanner including a motor mounted to rotate the deflecting means, the method comprising varying a scanning speed of the scanner for collecting a scanning light beam reflected from the scanned barcode label. Converting the reflected light beam into an electrical signal representative of the occurrence of each bar or space; detecting the time of occurrence of the continuous bar and space; and the occurrence of the continuous bar and space. Detecting whether the detected occurrence time is greater than or less than the expected occurrence time by comparing the time with the expected occurrence time; Scanner scan speed change wherein the time between is less than the occurrence time of the appointment and a step of reducing the rotational speed of the motor. 2. A device for scanning a bar code label consisting of a bar and a space at a variable speed, said device for generating a scanning light beam, and reflecting at least a part of said light beam toward said device. Rotating means for deflecting the scanning light beam to traverse the bar code label, and reflection means for controlling the pointing speed of the light beam directed to traverse the bar code label. A drive means for rotating and a processing means coupled to the drive means for controlling the rotational speed of the drive means in response to the distance between the continuous bar and the space scanned, Device for scanning at variable speed, characterized in that the rotational speed is reduced when the distance between them is at a minimum value.